from django.conf import settings
from django.core.paginator import Paginator
from django.db.models import Count
from django.shortcuts import get_object_or_404, redirect
from django.template.response import TemplateResponse
from django.urls import reverse

from wagtail import hooks
from wagtail.admin.auth import user_has_any_page_permission, user_passes_test
from wagtail.admin.navigation import get_explorable_root_page
from wagtail.admin.ui.side_panels import PageSidePanels
from wagtail.models import Page, UserPagePermissionsProxy


@user_passes_test(user_has_any_page_permission)
def index(request, parent_page_id=None):
    if parent_page_id:
        parent_page = get_object_or_404(Page, id=parent_page_id)
    else:
        parent_page = Page.get_first_root_node()

    # This will always succeed because of the @user_passes_test above.
    root_page = get_explorable_root_page(request.user)

    # If this page isn't a descendant of the user's explorable root page,
    # then redirect to that explorable root page instead.
    if not (parent_page.pk == root_page.pk or parent_page.is_descendant_of(root_page)):
        return redirect("wagtailadmin_explore", root_page.pk)

    parent_page = parent_page.specific

    user_perms = UserPagePermissionsProxy(request.user)
    pages = (
        parent_page.get_children().prefetch_related("content_type", "sites_rooted_here")
        & user_perms.explorable_pages()
    )

    # Get page ordering
    ordering = request.GET.get("ordering", "-latest_revision_created_at")
    if ordering not in [
        "title",
        "-title",
        "content_type",
        "-content_type",
        "live",
        "-live",
        "latest_revision_created_at",
        "-latest_revision_created_at",
        "ord",
    ]:
        ordering = "-latest_revision_created_at"

    if ordering == "ord":
        # preserve the native ordering from get_children()
        pass
    elif ordering == "latest_revision_created_at":
        # order by oldest revision first.
        # Special case NULL entries - these should go at the top of the list.
        # Do this by annotating with Count('latest_revision_created_at'),
        # which returns 0 for these
        pages = pages.annotate(
            null_position=Count("latest_revision_created_at")
        ).order_by("null_position", "latest_revision_created_at")
    elif ordering == "-latest_revision_created_at":
        # order by oldest revision first.
        # Special case NULL entries - these should go at the end of the list.
        pages = pages.annotate(
            null_position=Count("latest_revision_created_at")
        ).order_by("-null_position", "-latest_revision_created_at")
    else:
        pages = pages.order_by(ordering)

    # Don't paginate if sorting by page order - all pages must be shown to
    # allow drag-and-drop reordering
    do_paginate = ordering != "ord"

    # We want specific page instances, but do not need streamfield values here
    pages = pages.defer_streamfields().specific()

    # allow hooks defer_streamfieldsyset
    for hook in hooks.get_hooks("construct_explorer_page_queryset"):
        pages = hook(parent_page, pages, request)

    # Annotate queryset with various states to be used later for performance optimisations
    if getattr(settings, "WAGTAIL_WORKFLOW_ENABLED", True):
        pages = pages.prefetch_workflow_states()

    pages = pages.annotate_site_root_state().annotate_approved_schedule()

    # Pagination
    if do_paginate:
        paginator = Paginator(pages, per_page=50)
        pages = paginator.get_page(request.GET.get("p"))

    show_ordering_column = request.GET.get("ordering") == "ord"

    side_panels = PageSidePanels(
        request,
        parent_page.specific,
        in_explorer=True,
        preview_enabled=False,
        comments_enabled=False,
    )

    context = {
        "parent_page": parent_page.specific,
        "ordering": ordering,
        "side_panels": side_panels,
        "pages": pages,
        "do_paginate": do_paginate,
        "locale": None,
        "translations": [],
        "show_ordering_column": show_ordering_column,
        "show_bulk_actions": not show_ordering_column,
        "show_locale_labels": False,
    }

    if getattr(settings, "WAGTAIL_I18N_ENABLED", False):
        if not parent_page.is_root():
            context.update(
                {
                    "locale": parent_page.locale,
                    "translations": [
                        {
                            "locale": translation.locale,
                            "url": reverse(
                                "wagtailadmin_explore", args=[translation.id]
                            ),
                        }
                        for translation in parent_page.get_translations()
                        .only("id", "locale")
                        .select_related("locale")
                    ],
                }
            )
        else:
            context["show_locale_labels"] = True

    return TemplateResponse(request, "wagtailadmin/pages/index.html", context)
